A Self-Powered Camera

One of 10 innovations to win a 2016 Invention Award

By Alyssa Favreau | Published May 5, 2016 5:05 PM

The eternal camera. Jane Nisselson, Columbia Engineering

Eternal Camera

The eternal camera was invented by Shree K. Nayar, Mikhail Fridberg, and Daniel C. Sims at Columbia University.

At first glance, the boxy “eternal camera” looks like an old daguerreotype device. But appearances are deceiving. This is something new—a camera that powers itself.

The computer vision lab at Columbia University, led by computer scientist Shree K. Nayar, created this ever-lasting camera by making photodiodes—devices that convert light into electricity —do double duty. In digital cameras, photodiodes measure light. In solar panels, they harvest energy. The eternal camera’s photodiodes do both jobs. This enables the camera to generate enough power to take photos forever—as long as there’s light available.

Nayar’s team began by building just one double-duty photodiode. Mounted on a robot that slowly moved it in a grid, it captured an entire picture one pixel at a time, which took about an hour. The current iteration of the camera incorporates 1,200 pixels and takes a photo every second, displaying the images on an external monitor.

The group next plans to reduce the camera’s size while increasing its speed and resolution. That way it could be used for specialty projects where size and access to power are concerns: to track wildlife as part of conservation projects, to use less power on space-exploration missions, or to provide round-the-clock security.

For Nayar, the camera’s appeal goes beyond its technical accomplishments. “There’s a romantic aspect to this,” he says. “To have anything that can produce information without consuming power, that can go on forever— it’s a powerful concept.”

Eternal Camera Illustration

An exploded view of the eternal camera

How It Works

The eternal camera’s image sensor uses 1,200 photodiodes in a 30-by-40 array.
Each photodiode measures the light that passes through a lens and turns it into an electrical signal, which represents a single pixel. Combined, the signals create an image—just as they do in a standard camera.
Unlike conventional cameras, each of the eternal camera’s photodiodes are wired into a special circuit, which takes some of the electricity produced from the absorbed light and stores it in a capacitor to power itself.